topic Re: Challenge #135: Locker Problem in Weekly Challenges

Challenge #135: Locker Problem

JoeM — Tue, 13 Sep 2022 14:36:07 GMT

Thank you for participating in the Grand Prix challenges last week!

Next week's challenge will be posted during @NicoleJohnson's Inspire Europe Weekly Challenge (10:30AM on Wednesday 10/10)! Finally, those on GMT challengers will finally have first crack at the challenge. Unless @patrick_digan wakes up at 5:30AM Eastern.

Onto this week's challenge!

There are 1000 lockers in a high school with 1000 students. The problem begins with the first student opening all 1000 lockers; the second student closes lockers 2,4,6,8,10 and so on to locker 1000; the third student changes the state (opens lockers closed, closes lockers open) on lockers 3,6,9,12,15 and so on; the fourth student changes the state of lockers 4,8,12,16 and so on. This goes on until
every student has had a turn.

When all 1,000 students have finished, which locker doors are open?

Re: Challenge #135: Locker Problem

NicoleJohnson — Mon, 01 Oct 2018 18:35:02 GMT

Back to school! My solution :)

My favorite - iterative macros!! This was a fun one... and ended up with a pleasantly low number of tools!

Workflow - Fun using the Generate Rows tool without an input, rarely have had opportunities to do that.
Locker Macro, using a Floor formula to determine which lockers to open/close!

Cheers,

Re: Challenge #135: Locker Problem

bdaniels — Mon, 01 Oct 2018 18:36:14 GMT

Kind of messy

Re: Challenge #135: Locker Problem

patrick_digan — Mon, 01 Oct 2018 19:14:31 GMT

I've got my alarm set for 5:30 am next wednesday!

I went with the iterative macro approach

There are some really creative solutions when @Ned posted this problem a few years ago.

Re: Challenge #135: Locker Problem

ggruccio — Mon, 01 Oct 2018 19:58:53 GMT

I'm imagining this is a very loud exercise!

Helps to use the modulo (mod) function in the macro.

Re: Challenge #135: Locker Problem

danilang — Mon, 01 Oct 2018 21:52:58 GMT

Fun challenge.

Ok, all you Math gurus. Can anyone explain why, iteratively applying the sieve of Eratosthenes, should generate that particular, very familiar, sequence of numbers? Is all of math beautifully connected at a level just below what common folk like me can see?

And what's up with Euler's Identity anyway

Dan

Re: Challenge #135: Locker Problem

GarthG — Mon, 01 Oct 2018 23:45:00 GMT

Went macro-less this week!

Re: Challenge #135: Locker Problem

jasperlch — Tue, 02 Oct 2018 02:44:47 GMT

Solution attached.

Re: Challenge #135: Locker Problem

KOBoyle — Tue, 02 Oct 2018 06:16:41 GMT

Solution attached.

Used an iterative macro with an app to allow for user specified locker count.

Re: Challenge #135: Locker Problem

philipmannering — Tue, 02 Oct 2018 07:07:08 GMT

I used the R tool to loop over all the lockers and change their state.

Workflow

Re: Challenge #135: Locker Problem

Alt_JP — Tue, 02 Oct 2018 13:37:20 GMT

Found a solution without using input files or macros. Takes 0.8 sec to run on my machine.

Re: Challenge #135: Locker Problem

DavidP — Tue, 02 Oct 2018 12:56:10 GMT

I discovered the Modulo function and what it does!!! And iterative macros are now a little less scary... My solution attached.

However, that was my 2nd attempt. With my 1st attempt I tried to update a sample tool with the IterationNumber as shown below, but for some reason it wouldn't work - it doesn't seem to update the value of N in the sample tool. Does anyone know what I'm doing wrong?

Re: Challenge #135: Locker Problem

patrick_digan — Tue, 02 Oct 2018 13:17:38 GMT

@DavidP I'm not certain, but I don't think any of the interface tools (action tool included) are able to use/update the IterationNumber.

Re: Challenge #135: Locker Problem

clant — Tue, 02 Oct 2018 13:34:29 GMT

I couldnt work out what i was doing wrong until i actually read the instructions properly. I originally worked it so every person would change the status of every locker higher than them not just multiples.

Re: Challenge #135: Locker Problem

StevenBetts — Tue, 02 Oct 2018 13:54:50 GMT

Was pleased to find a solution without having to use macros - I still haven't quite gotten my head around those yet!

Re: Challenge #135: Locker Problem

ponraj — Tue, 02 Oct 2018 15:13:05 GMT

Here is my version.

Main workflowIteration workflow

Re: Challenge #135: Locker Problem

sh0kat — Tue, 02 Oct 2018 17:40:05 GMT

Here's my solution :)

Re: Challenge #135: Locker Problem

Ladarthure — Tue, 02 Oct 2018 17:45:34 GMT

My solution without macro

Re: Challenge #135: Locker Problem

CharlieS — Tue, 02 Oct 2018 19:41:10 GMT

Re: Challenge #135: Locker Problem

kat — Tue, 02 Oct 2018 21:57:54 GMT